Referring to FIGS. 1 and 2, a conventional suction cup device includes an elastically deformable suction disk 1, a pressing member 2 connected to the suction disk 1, a cover member 3 sleeved on the pressing member 2 and connected to the suction disk 1, and a spring 4 abutting between the cover member 3 and the pressing member 2. The suction disk 1 has a bottom surface 101 that is concave, and a cavity 102 formed in the bottom surface 101. To use the conventional suction cup device, the suction disk 1 is brought to abut against a support surface (not shown), and a pressing force is exerted on the pressing member 2, so that the suction disk 1 is deformed into a flat shape, as shown in FIG. 2. Air in the cavity 102 is squeezed out therefrom so as to flatten the cavity 102 and adhere the bottom surface 101 to the support surface. At this time, a low pressure state exists between the bottom surface 101 and the adhered support surface.
The action of the spring 4 is intended to generate a reverse force between the cover member 3 and the pressing member 2, and by using the biasing force of the spring 4, a periphery of the cover member 3 can press against a periphery of the suction disk 1. However, after using the conventional suction cup device for some time, air may penetrate between the bottom surface 101 and the adhered support surface. Through the biasing action of the suction disk 1, the suction disk 1 is restored to its original state, as shown in FIG. 1. Thus, the suction force of the suction disk 1 is deteriorated. If a user can discover it in time, he/she can press the pressing member 2 again so as to flatten the bottom surface 101 of the suction disk 1 and squeeze the air out therefrom. But if not, the conventional suction cup device is likely to fall off from the adhered support surface.
Referring to FIGS. 3 and 4, another conventional suction cup device, as disclosed in Taiwanese Patent No. M380400, includes a protrusion 5, a reinforcing member 6 and a suction member 7. In a normal state, a gap 8 is formed between the reinforcing member 6 and the suction member 7. In use, the protrusion 5 is depressed, the reinforcing member 6 and the suction member 7 are elastically deformed, and air in the reinforcing member 6 and air in the suction member 7 are squeezed out, so that the gap 8 disappears, and the reinforcing member 6 and the suction member 7 are adhered flatly to a support surface (S), as shown in FIG. 4. As such, the speed of return pressure can be reduced through the reinforcing member 6 and the suction member 7. However, after using the aforesaid conventional suction cup device for some time, air may still penetrate between the reinforcing member 6 and the suction member 7, so that a user must remove and depress again the suction cup device against the support surface (S). Hence, use of this suction cup device is unreliable.
When use in large-scale machinery, some special suction cup devices use vacuum pumps and switchable solenoid valves for adhering a workpiece to be transported, but their structures are rather complicated and must cooperate with a variety of electronic control facilities, which are not suitable to be applied in suction disks used in daily life.